When I checked the temperature in Chicago one day last winter, it was six degrees, and the way I look at it, the only six degrees worthy of consideration is six degrees of separation from Kevin Bacon, whom I saw in the airport a few days prior. (By the way, he looked thinner than I expected.) But that is a wild digression from the subject at hand, which is extremely low temperatures, the kind that plagued much of the U.S. last winter, no doubt the result of global warming. What does this have to do with you and your car? Simply this: In single-digit winter temperatures across the country, your vehicle's oil and filter are put to the test in ways you might never imagine.

"The most obvious point to consider when temperatures dip very low is your choice of motor oil and filter," said Ramon Nunez, spokesman for Purolator Filters.

While many people understand that choosing an oil with the proper viscosity is critical, especially in the winter, they might not know that winter puts added strain on other parts of their car's lubrication system, too. "Many people are surprised to learn that winter weather also puts extra demands on your oil filter," Nunez said.

At 20 degrees F, most oils have the thickness of maple syrup. So when your engine first starts up, your engine's oil pump forces cold, thick oil through all the passages in your engine, including those in your oil filter. A number of factors determine if the oil will find its way through the filter to provide lubrication to your engine, while particulates are filtered out.

Nunez points out three specific design elements engineered into filters to help them perform properly in winter weather: structural integrity, internal valving and the media of the filter itself.

Upon startup in cold weather, your engine will experience an initial surge of pressure. This pressure could compromise oil filters at their weakest point and manifest itself as a blown-out sealing ring, a split crimp or even a burst canister if the filter is not constructed robustly enough. Any of these can cause catastrophic engine failure. Premium oil filters (like Purolator's PureONE) are built and tested to withstand virtually all real-world pressure spikes.

Internal valving is equally critical. Purolator engineers have developed a special spring-loaded bypass valve so that if the filter goes unchanged for an extended period of time and is blocked with debris, unfiltered oil can flow to the engine, providing at least some lubrication, albeit with dirty oil. Instead of a reliable coil spring, some filter manufacturers scrimp by substituting "spring" steel that may not return to its original shape after cycling. The result can be unfiltered oil for as long as the filter is in place, with potentially catastrophic results.

Finally, the filter must remove the smallest particles while offering the least resistance to oil flow. According to Nunez, premium oil filters, like Purolator's top-grade PureONE filter, are developed to hold as much as 13 grams of debris -- the equivalent of 31 standard size paper clips -- while still providing minimal resistance to oil flow. So when you specify the proper grade premium oil at your next oil change, also make certain you are specifying the installation of a premium-grade oil filter.

*DISCLAIMER*: The information contained in or provided through this site section is intended for general consumer understanding and education only and is not intended to be and is not a substitute for professional advice. Use of this site section and any information contained on or provided through this site section is at your own risk and any information contained on or provided through this site section is provided on an "as is" basis without any representations or warranties.